DESCRIPTION (adapted from the applicant's description): The long-term goal of this research is to better understand how circadian clocks work in eukaryotic cells, using Arabidopsis as a model system. Genetic approaches have revealed components of the circadian clock in Arabidopsis. Proposed studies will extend a mutant hunt using rhythmic bioluminescence in transgenic seedlings screened by high throughput automated monitoring of the circadian-regulated expression of CAB::luciferase construct. Several toc mutant genes, which are likely to encode central components of the Arabidopsis circadian system, will be cloned and characterized. Additionally, by crossing the luciferase fusion markers into available photoreceptor, phototransduction, and floral timing mutants, it is proposed to relate circadian function to previously defined pathways for photo-transduction and photoperiodic control of flowering. Ultimately, genes that are involved in many aspects of circadian timing will be cloned. Given the ubiquity of circadian-regulated physiology, the identification of common clock components may have an impact on understanding the mechanisms of circadian regulated functions in humans.